UtinniJeep

Hi Fellow Jeep Lovers!

I have a 1995 Jeep Cherokee Sport 4.0. Last year was the first year my Jeep has not passed smog. So I did what the smog tech told me to do. Get a new Cat. Bought a new aftermarket Cat and it didn't pass smog. Soooo...Went and flushed out all the liquids, new H2O sensor, New spark plugs and dis cap, Tried seafoam, And still won't pass!! The tech told me that the NOX is running too High. There was no Oil on the plugs. I'm in California. I'm at my wits end! Because my Jeep runs Great! Other than it won't pass Smog! My brother who works at a Jeep/Insert other cars here dealership told me the ONLY thing that will make it pass smog is a NEW In Stock Jeep Cat that of course is $1400 and up!And I'm on a budget. And I won't sell my Greenie!! Any Help would be Great! Thank you!

dmill89

Make sure the EGR valve and passages are clean and the valve is working correctly (NOX is mostly affected by the cat and EGR) .

Get ethanol-free gas if you can, e10 can raise NOX by up to 5%.

Make sure it is good and hot (drive 30+ min on the highway) before getting it tested, cats work better when they are hot and combustion is more complete which will lower all emissions levels including NOX.

I'm glad that here in PA pre-ODBII (pre-96) vehicles get a visual emissions inspection only (as long as you have a cat and no exhaust leaks you pass).

If all else fails move out of California (land of the eco-*****) J/K.

rawk krawler

No EGR on 95, I've got an aftermarket cat and I'm getting smogged as we speak lol.
I'll let you know my results.
Check every vacuum line, I had melted my gas tank vent line (runs behind the block)
Do you have a badly cracked manifold?

rawk krawler

Failed, high nox, lets see your numbers!

I'm going to get a new o2

F1Addict

Also, check the rubber hoses going to and from the evap canister (passenger side firewall, at least on an '89). My low speed (15 mph) NOx numbers were also high (703 with a max allowable 711!) but my high-speed (25 mph) numbers were exemplary (143 ppm with max allowable 613 ppm). The technician suggested that replacing my cracked and weathered evap lines would vastly improve the low-speed number.

These numbers disappointed me since I'd had the car for two years and this was the first time I'd had to smog it. I have the numbers from the previous smog, provided by the previous owner as part of the sale. Those numbers are almost too good to believe. The previous owner only performed the minimum maintenance (changed the oil). Since buying, I have replaced the fuel filter, spark plugs, spark plug wires, CPS, installed 703 injectors, replaced the air filter, all vacuum lines, and performed all routine maintenance yet the numbers are just horrible compared to the 2011 test. I'm at a bit of a loss.

Here are the 2011 numbers...



...and my 2013 results...

rawk krawler

Replaced o2, getting tested currently, next ill be doing manifold, then cat.

rawk krawler

My numbers

F1Addict

Are those before or after O2 sensor replacement?

rawk krawler

Before, I'll have the after number in a few minutes.

rawk krawler

OP where did you buy your cat, and was it a California approved version?
Still waiting for those numbers!

UtinniJeep

There are two smog tests here with different numbers. But both fail. After I changed out the O2 sensor it went down alot but still didn't pass smog. I can't find that paper. Frustration must of lost it! But here are the first 2 fails.

UtinniJeep

Here is the other test. It wouldn't let me download both. Thanks for all your help everyone!

F1Addict

Are you using the 50-state Magnaflow cat? High NOx readings are caused by a lean condition or a bad cat. You've replaced the cat and the O2 sensor so two primary culprits have been eliminated. Other causes are the aforementioned evap hoses, vacuum leak, faulty manifold temp sensor, excessive underhood temperature and finally carbon deposits significant enough to reduce overall combustion chamber volume. That last one is unlikely except in poorly maintained, high-mileage rigs.

jake92

Do you have vacuum leaks?
How hot is the Jeep running?
How is the EGR?
Was the cat a name brand or a no name?
What O2 sensor was put in?

rawk krawler

No EGR lol. 95.

I'm personally replacing my map sensor tomorrow morning and re-testing, I will show my results!